Background Rheumatoid arthritis (RA) patients have a higher prevalence of falls compared with the healthy population. Several risk factors of falls in RA have been postulated, including high disease activity, low balance, muscle weakness and non-treatment with biologics. Aim of the work We investigated our hypothesis that the sonographically detected ankle and foot changes in RA patients can predict falls in this population. To our knowledge, no previous study had investigated this before. Methods In a total of 101 RA patients, we performed assessments of disease activity, disability level, gait speed, balance status, clinical examination of ankle and foot and an MSUS assessment of the ankle and foot joints and tendons as possible risk factors of falls. Results The Berg balance test had the highest fall-predicting power (71.3%), followed by a gait speed test and restricted range of motion (ROM) of the Rt. subtalar joint, each with a predictive power of 70.3%. Of the sonographic findings, erosion of the first metatarsophalangeal (MTP) joint was the most accurate fall predictor, followed by erosion of the talonavicular joint and tenosynovitis of the ankle dorsal flexors with an area under the curve of 0.656, 0.642 and 0.614, respectively. Conclusion The use of the MSUS as an adjunct objective method for predicting falls in RA patients has not been studied before. It was found that clinical foot and balance testing was a superior and easier way of predicting falls in RA patients than using ultrasonography.